Extrinsic Fabry-Perot Interferometer (EFPI) sensors can be used to measure environmental phenomena such as temperature, pressure, acceleration, etc., by coupling the EFPI sensor to the desired environment. For example, a diaphragm within the sensor may be used to physically couple external pressure changes to a reflective surface of an optical fiber within the EFPI cavity. By interrogating the cavity with light, a signal may be generated that corresponds to the external pressure changes. Thus, the retrieved signals from these sensors typically correspond to optical interference fringe intensity variations corresponding to the measured phenomena as the sensor is subjected to environmental changes.
Among the challenges faced in making such measurements with an EFPI sensor is that fluctuations of other parameters in the system can result in measurement errors. For example, fluctuations in the light source intensity can affect the signal. Furthermore, spurious reflections from fusion joints in the optical fiber, changes in the index of refraction of the fiber as a function temperature, stress induced changes resulting from the expansion and contraction of the optical fiber and its mating materials as a function of temperature, mismatches in the coefficient of thermal expansion of mating materials, etc., can further influence the measurement. A need exists to reduce or eliminate measurement errors while protecting the various components of the sensors.